Hedgehogs and the pop-off syndrome



On December 1st, 2024, a young male hedgehog (Erinaceus europaeus) was found stuck in the net of a vegetable garden. The hedgehog was cold and dehydrated, but still alive. He was taken to an animal shelter where it turned out that the hedgehog’s spines had folded over its pelvis. This made the animal caretakers suspect a case of the pop-off syndrome (see figure). The animal was too weak to treat, and was therefore put down. The DWHC conducted a pathological examination which showed that the hedgehog had an inflammation of the back muscle. This inflammation fits the symptoms of the so-called pop-off syndrome. In addition, the hedgehog had parasitic pneumonia and parasites were found in the intestine.

The pop-off syndrome

When a hedgehog rolls itself up, it uses, among other muscles, the ‘purse-string’ muscle (M. orbicularis). This muscle runs along the line between the spiney skin and the soft fur. It works similarly to the pull string of a garbage bag. When the hedgehog contracts this muscle, it pulls the skin holding the spines around the pelvis, legs, and head, so that the body is completely surrounded by the spines and is safe from predators.

During extreme muscle exertion, the ‘purse-string’ muscle can fold up over the pelvis and get stuck: the pop-off syndrome (Bexton, 2019). The muscle goes into a spasm, which leaves the hedgehog unable to roll up and causes the pelvis and hind legs to remain visible. This is very dangerous for the animal. The pop-off syndrome occurs in situations of extreme stress, such as a collision with a vehicle or getting stuck in a net as with this hedgehog (Bexton, 2016). To help the muscle relax again, a veterinarian can anesthetize the hedgehog’s muscle and massage it back to the other side of the pelvis (Bexton, 2019). As the general health condition of this hedgehog was already too poor, this was unfortunately no longer an option in this case.

Literature

Bexton, S. (2016). Hedgehogs. In BSAVA manual of wildlife casualties (pp. 117-136). BSAVA Library.
Bexton, S., & Couper, D. (2019). Veterinary care of free‐living hedgehogs. In Practice, 41(9), 420-432.

Banner hedgehog: © Bas Worm